Modern large block cave mines require a significant time to develop and a very significant early investment. Both of these factors make their financial success in terms of net present value extremely sensitive to the speed at which they can be brought on stream. Deep cave mines require shaft access and the development of this shaft access forms the initial part of the mine development and therefore is directly on the project critical path i.e. until the initial shafts are completed no other underground development activity can be commenced.
Traditional shaft sinking operations are carried out by drilling and blasting to excavate material to form a hole and removing the excavated material by a mucking system by which the excavated material is picked up and deposited in kibbles which are hoisted to the surface on cables run to head gear and a winder installed at the surface of the mine. This mucking operation requires skilled operators and is inherently dangerous to miners required to guide and operate equipment at the bottom of the shaft as it is being formed. Moreover, the speed at which the excavated material can be removed is limited by the need to cease operations for drilling and blasting, the difficulty of loading variable sized material into the kibbles and the limited speed at which the kibbles can be hoisted and lowered as they tend to move about on the very long lengths of cable as sinking progresses.
There have been proposals to increase the speed at which sinking can progress by using earth boring machinery. For example, U.S. Pat. No. 3,965,995 of Sugden which discloses a proposal to use a cutter wheel which rotates about a horizontal tubular support, where the cutting are directed into the tubular support to be received by an endless bucket which carries them up to a discharge station. Another example is U.S. Pat. No. 4,589,502 of Salter et al which discloses a proposal to use a shaft sinking apparatus which employs an earth boring machine having a rotary cutting head and a bucket conveyor for carrying cuttings to a feed bin installed on the boring machine from which the cuttings can be fed into a skip which is lifted by a crane to the ground surface. However, these prior art proposals still involve the direct filling of kibbles, buckets or skips and the operational speed and capacity from such systems is thus limited by having such filling devices on station, ie if there is no filling device at the discharge station for such earth boring machinery, the machines must temporarily cease cutting until another filling device is available. The present invention enables development of a more robust and effective removal system which allows the continued supply of excavated material to continue from such machines even if filling devices are not on station.